1. Field of the Invention
The present invention relates generally to liquid crystal display (LCD) devices, and more particularly to color LCD devices for use with a touch-sensitive pointing input device and an image display method thereof.
2. Description of the Prior Art
Through the trend of complexity in computerization as to diversity of information in the recent past, portable or “handheld” electronic information management tools including personal digital assistants (PDAs) have found increasing applications due to advantages such as small size and light weight. In the thrust to achievement of such advanced handheld information management tools, the pen-input scheme is becoming more important for permission of direct entry of input data or instructions by use of a touch-sensitive coordinate pointing input device known as a “pen” pointer in the art through an associated tough-screen display panel in such a simple and easy way that allows users to “write down” by hand on a memo pad. As such pen-input scheme, several techniques have been proposed until today, including a technique of laminating a pen-input panel (tablet panel) on an associated display panel, a technique of common use of a display panel also as the tablet, and others.
One typical pen-input scheme incorporating the former technique has been disclosed in, for example, Published Unexamined Japanese Patent Application (PUJPA) No. 58-200384 and also in PUJPA No. 7-175591. With the prior art, an input tablet is constituted from two light transmissive substrates having lateral and longitudinal elongate electrodes for position detection. The substrates may be made of glass, polycarbonate or other polymer material. When the pen pointer is manually operated by users to draw a desired locus thereon while rendering the pen pressed onto the surface of the tablet at a tip end thereof, a coordinate detector circuit operates to sense or detect corresponding coordinates of a drawing position every time the coordinates change. A control circuit is responsive to receipt of such detected coordinates for providing adequate image data indicative of character set or graphics as pursuant to the coordinate detection result, allowing a resultant drawing image to be visually indicated on the LCD panel under the control of LCD driver circuitry.
Unfortunately, the prior art LCD devices suffer from the lack of ability to process color images for display. A need has therefore been felt for a color-image displayable LCD device for use with the pen-pointer input device permitting direct entry of input data and instructions.